Investigation of morphotropic phase boundaries in PIN–PSN–PT relaxor ferroelectric ternary systems with high T_r-t and T_c phase transition temperatures

New morphotropic phase boundary (MPB) compositions with relatively high T_cs were projected in Pb(In_1/2Nb_1/2)O₃–Pb(Sc_1/2Nb_1/2)O₃–PbTiO₃ (PIN–PSN–PT) solid solution based on the perovskite tolerance factor, and were experimentally confirmed. The phase structure, dielectric, pyroelectric, piezoelectric and ferroelectric properties of PIN–PSN–PT ceramics were investigated. The rhombohedral–tetragonal phase transition temperatures T_r-t on the order of 189–210 °C, Curie temperatures T_c on the order of 274–285 °C and piezoelectric coefficients d₃₃ in the range of 310–360 pC/N, were achieved in xPIN– (1 − x)PSN–0.37PT (x = 0.15–0.23) ceramics, demonstrating a promising relaxor–PbTiO₃ system with high phase transition temperatures. In addition, the maps of T_c, T_r-t, d₃₃ and ε_r with respect to composition were established, based on which, a clear direction for composition screening in future crystal growth of the PIN–PSN–PT system was given.